Valve for a vehicle suspension system

ABSTRACT

A valve assembly for a suspension system includes a housing including a first port, a second port, and a third port, the housing defining a first flow path extending between the third port and the first port and a second flow path extending between the third port and the second port. The valve assembly further includes a first check valve having a first crack pressure positioned within the housing along the first flow path and a second check valve having a second crack pressure positioned within the housing along the second flow path. A difference between the first crack pressure and the second crack pressure provides a corresponding difference in pressures at the first port and the second port.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 13/792,153,filed Mar. 10, 2013, which claims the benefit of U.S. Provisional PatentApplication No. 61/615,710, filed Mar. 26, 2012, both of which areincorporated herein by reference in their entireties.

BACKGROUND

The present application relates to suspension systems for vehicles. Morespecifically, the present application relates to a valve for asuspension system. Suspension systems may include springs that have agas stored therein. The weight of the sprung mass of the vehiclecompresses the gas within the spring. The pressure of the gas within thespring is related to the weight of the vehicle, and the cross-sectionalarea of the spring chamber, the temperature of the operatingenvironment, and still other considerations. The gas within the springis charged to an initial pressure, which relates to an initial rideheight. As payload is added to the vehicle, the gas within the spring isfurther compressed, and the ride height of the vehicle decreases.Similarly, the pressure of the gas within the spring changes with thetemperature of the operating environment thereby altering the rideheight of the vehicle.

Traditional gas springs modulate ride height with multiple pneumaticsources that apply pressurized fluid to the spring. Other systemsutilize complex control systems to maintain an appropriate pressure ofthe gas within the spring. Such systems are expensive, require numerousadditional components, and introduce a failure mode by relying onintermediate electronic controls to charge the spring to a particularpressure.

SUMMARY

One embodiment of the invention relates to a valve assembly for asuspension system that includes a housing including a first port, asecond port, and a third port, the housing defining a first flow pathextending between the third port and the first port and a second flowpath extending between the third port and the second port. The valveassembly further includes a first check valve having a first crackpressure positioned within the housing along the first flow path and asecond check valve having a second crack pressure positioned within thehousing along the second flow path. A difference between the first crackpressure and the second crack pressure provides a correspondingdifference in pressures at the first port and the second port.

Another embodiment of the invention relates to a suspension assembly fora vehicle that includes a gas spring and a valve assembly. The gasspring includes a tubular housing, a plunger positioned within thetubular housing, the plunger and an inner surface of the tubular housingdefining a spring volume, a reservoir including a housing that definesan inner volume and a flexible member coupled to the housing, theflexible member separating the inner volume into a working volume and acontrol volume, and a conduit coupling the tubular housing to thereservoir such that the spring volume is in fluid communication with theworking volume. The valve assembly includes a first check valve having afirst crack pressure positioned along a first flow path between thespring volume and a flow device port and a second check valve having asecond crack pressure positioned along a second flow path between thecontrol volume and the flow device port. The valve assembly provides anoffset pressure between the spring volume and the control volume tomaintain a response curve of the gas spring for different ride heightsof the vehicle.

Yet another embodiment of the invention relates to a method for changinga ride height of a vehicle that includes providing a gas springincluding a housing that defines a spring volume and an accumulator thatdefines a control volume, providing a valve assembly including a portand a plurality of check valves having different crack pressures,exposing the port to a pressurized fluid associated with a flow device,and maintaining a pressure differential between the spring volume andthe control volume, the pressure differential corresponding to adifference in the crack pressures of the plurality of check valves.

The invention is capable of other embodiments and of being carried outin various ways. Alternative exemplary embodiments relate to otherfeatures and combinations of features as may be recited in the claims.

BRIEF DESCRIPTION OF THE FIGURES

The disclosure will become more fully understood from the followingdetailed description, taken in conjunction with the accompanyingfigures, wherein like reference numerals refer to like elements, inwhich:

FIG. 1 is an elevation view of an axle assembly including a suspensionsystem, according to an exemplary embodiment.

FIG. 2 is an elevation view of a suspension system an axle assembly,according to an exemplary embodiment.

FIG. 3 is a side plan view of a gas spring and a valve assembly,according to an exemplary embodiment.

FIG. 4 is an elevation view of a valve assembly, according to anexemplary embodiment.

FIGS. 5-7 are elevation views of a valve assembly defining a pluralityof flow paths, according to an exemplary embodiment.

FIG. 8 is a plan view of a valve assembly, according to an exemplaryembodiment.

FIGS. 9-11 are sectional views of a valve assembly, according to anexemplary embodiment.

FIGS. 12-14 are schematic views of a suspension assembly having a gasspring and a valve assembly, according to an exemplary embodiment.

FIG. 15 is a schematic diagram of pressure drop versus flow rate for acheck valve, according to an exemplary embodiment.

DETAILED DESCRIPTION

Before turning to the figures, which illustrate the exemplaryembodiments in detail, it should be understood that the presentapplication is not limited to the details or methodology set forth inthe description or illustrated in the figures. It should also beunderstood that the terminology is for the purpose of description onlyand should not be regarded as limiting.

Referring to the exemplary embodiment shown in FIG. 1, an axle assembly110 is configured to be included as part of a vehicle. The vehicle maybe a military vehicle, a utility vehicle (e.g., a fire truck, a tractor,construction equipment, a sport utility vehicle, etc.), or still anothertype of vehicle. As shown in FIG. 1, axle assembly 110 includes adifferential 112 coupled to a half shaft 114. As shown in FIG. 1, halfshaft 114 is coupled to a wheel-end assembly 116. The wheel-end assembly116 may include brakes, a gear reduction, steering components, a wheelhub, a wheel, a tire, and other features. According to an exemplaryembodiment, the differential 112 is configured to be coupled with adrive shaft of the vehicle. Such a differential 112 may receiverotational energy from a prime mover (e.g., a diesel engine, a gasolineengine, an electric motor, etc.) of the vehicle. The differential 112then allocates torque provided by the prime mover between the halfshafts 114 of the axle assembly 110. The half shafts 114 deliver therotational energy to each wheel-end assembly 116. According to analternative embodiment, each wheel-end assembly 116 includes a primemover (e.g., the axle assembly 110 includes electric motors that eachdrive one wheel).

According to an exemplary embodiment, the axle assembly 110 includes asuspension system 118 that couples the chassis of the vehicle towheel-end assembly 116. In some embodiments, the chassis includes a pairof opposing frame rails, and the suspension system 118 engages theopposing frame rails through side plate assemblies. In otherembodiments, the chassis is a hull, a capsule, or another type ofstructural member. According to an exemplary embodiment, the suspensionsystem 118 includes a spring, shown as gas spring 120, and a damper,shown as hydraulic damper 122. As shown in FIG. 1, the gas spring 120and the hydraulic damper 122 are coupled in parallel to a lower supportmember, shown as lower swing arm 126. According to an exemplaryembodiment, the wheel-end assembly 116 is coupled to lower swing arm 126and an upper support member, shown as upper swing arm 124.

According to an exemplary embodiment, the vehicle is configured foroperation on both smooth (e.g., paved) and uneven (e.g., off-road,rough, etc.) terrain. As the vehicle travels over uneven terrain, theupper swing arm 124 and the lower swing arm 126 guide the verticalmovement of the wheel-end assembly 116. A stop, shown as cushion 128,provides an upper bound to the movement of the wheel-end assembly 116.It should be understood that axle assembly 110 may include similarcomponents (e.g., wheel-end assemblies, suspension assemblies, swingarms, etc.) for each of the two opposing lateral sides of a vehicle.

Referring next to the exemplary embodiment shown in FIG. 2, thesuspension system 118 includes various components configured to improveperformance of the vehicle. As shown in FIG. 2, gas spring 120 is ahigh-pressure gas spring. According to an exemplary embodiment, thesuspension system 118 includes a pump, shown as high-pressure gas pump130, that is coupled to gas spring 120. In some embodiments, suspensionsystem 118 includes a plurality of high-pressure gas pumps 130 eachcoupled to a separate gas spring 120. In other embodiments, thesuspension system 118 includes fewer high-pressure gas pumps 130 thangas springs 120. According to an exemplary embodiment, the gas springand the pump include gas made up of at least 90% inert gas (e.g.,nitrogen, argon, helium, etc.). The gas may be stored, provided, orreceived in one or more reservoirs (e.g., tank, accumulators, etc.).During operation, the high-pressure gas pump 130 selectively providesgas, under pressure, to at least one of the gas spring 120 and thereservoir. In some embodiments, at least one of the gas springs 120 andthe hydraulic dampers 122 receive and provide a fluid (e.g., gas,hydraulic fluid) to lift or lower the body of the vehicle with respectto the ground thereby changing the ride height of the vehicle.

Referring next to the exemplary embodiment shown in FIG. 3, a spring,shown as gas spring 300, includes a tubular member 312 coupled to a rod314. As shown in FIG. 3, tubular member 312 includes a sidewall 320, anend cap 316 that is coupled to a first end of sidewall 320, and a rodend 318 that is coupled to an opposing end of sidewall 320. According toan exemplary embodiment, sidewall 320 is cylindrical. According to analternative embodiment, sidewall 320 has a different geometry (e.g.,rectangular, square, hexagonal, etc.). A piston, shown as plunger 326,is coupled to an end of rod 314 and disposed within the inner volume oftubular member 312. A spring volume, shown as spring chamber 328, isformed within tubular member 312 by end cap 316, an inner surface ofsidewall 320, and plunger 326. According to an alternative embodiment,spring chamber 328 is at least partially formed within a portion of rod314. By way of example, spring chamber 328 may span both an inner volumebetween sidewall 320, end cap 316, and a face of plunger 326 and also aninner portion of rod 314.

According to an exemplary embodiment, a fluid (e.g., nitrogen, anothergas, etc.) is disposed within spring chamber 328 of gas spring 300. Itshould be understood that gas spring 300 may be implemented as part of avehicle suspension system. As the vehicle encounters an obstacle (e.g.,a positive obstacle, a negative obstacle, etc.) a wheel-end and othercomponents (e.g., a swing arm, etc.) of the vehicle suspension systemtranslate vertically. According to an exemplary embodiment, rod 314 iscoupled to the swing arm and tubular member 312 is coupled to thechassis (e.g., frame rail, hull, etc.) of the vehicle such that relativemovement occurs between tubular member 312 and rod 314 as the vehicleencounters the obstacle. Such relative movement increases or decreasesthe pressure of the fluid within spring chamber 328 as gas spring iscompressed or extended, respectively. Compression of gas spring 300stores kinetic energy from rod 314 and other suspension components aspotential energy in the fluid, and extension of gas spring 300 releasespotential energy stored within the fluid. relative movement betweentubular member 312 and rod 314 also changes the volume of spring chamber328, according to an exemplary embodiment. The fluid in spring chamber328 resists compression, thereby providing an opposing spring force. Themagnitude of the opposing spring force is a function of thecompressibility of the fluid, the area of the piston, the volume andgeometry of the chamber, and an initial state (e.g., initial pressure)of the fluid, among other factors.

According to an exemplary embodiment, gas spring 300 includes areservoir, shown as accumulator 330. As shown in FIG. 3, accumulator 330is positioned proximate to the tubular member 312 and rod 314.Accumulator 330 includes a housing, shown as shell 334, that defines aninner volume, according to an exemplary embodiment. A flexible member,shown as bladder 336, separates the inner volume of shell 334 into aworking volume, shown as working chamber 332, and a control volume,shown as control chamber 338. As shown in FIG. 3, working chamber 332 isformed by an inner surface of shell 334 and a first surface of bladder336, and control chamber 338 is formed by an inner surface of shell 334and a second, opposing surface of bladder 336. According to an exemplaryembodiment, a conduit 322 couples accumulator 330 to tubular member 312.A flow passage extends through conduit 322 and couples spring chamber328 of tubular member 312 to working chamber 332 of accumulator 330.

In some embodiments, spring chamber 328 is in gaseous communication withthe working chamber 332 such that a continuous body of gas extendsbetween spring chamber 328 and working chamber 332. No intermediatehydraulic fluid or mechanical element is included to transfer energyfrom the spring chamber 328 to the working chamber 332 or vice versa. Insome such embodiments, the only hydraulic fluid associated with the gasspring 300 is a thin film between the rod and cylinder that moves duringcompression or extension of the rod 314. Use of the continuous body ofgas for gaseous communication between spring chamber 328 and workingchamber 332 is intended to reduce frictional losses associated withenergy transfer between spring chamber 328 and working chamber 332, asmay otherwise occur with hydraulic or mechanical intermediate elements.In other contemplated embodiments, hydraulic or mechanical intermediateelements may be used.

A flow control device (e.g., a check valve, a deflected disk valve, apoppet, etc.) may be positioned within conduit 322 to limit the flow offluid between spring chamber 328 and working chamber 332. Such a flowcontrol device may be selectively operable thereby allowing for theactivation or deactivation of accumulator 330 (e.g., manually by a user,automatically as part of a control scheme, etc.). Spring chamber 328 issubstantially sealed when such a flow control device is not open (e.g.,to provide a gas spring having a first set of operatingcharacteristics). According to an alternative embodiment, conduit 322couples spring chamber 328 to another device (e.g., a pump, etc.).According to still another alternative embodiment, conduit 322 couplesspring chamber 328 to accumulator 330 and another device. Gas spring 300may have a single port that communicates with a pump and a reservoir ormay have separate ports for each component.

According to an exemplary embodiment, shell 334 is a rigid member andbladder 336 is flexible. The fluid within control chamber 338 ispressurized (e.g., by a pump, through exposure to higher-pressure fluidfrom a reservoir, etc.) such that bladder 336 is inflated. According toan exemplary embodiment, bladder 336 remains inflated while the pressureof the fluid within control chamber 338 is greater than the pressure ofthe fluid within working chamber 332. Relative movement between tubularmember 312 and rod 314 occurs as the vehicle encounters an obstacle. Byway of example, the pressure of the fluid within spring chamber 328increases as the vehicle encounters a positive obstacle.

According to an exemplary embodiment, the flow control device withinconduit 322 is open or conduit 322 does not include a flow controldevice, and the pressures of the fluid within working chamber 332 andspring chamber 328 are approximately equal. Gas spring 300 responds toan input from an obstacle at a first spring rate where the pressure ofthe fluid within spring chamber 328 and working chamber 332 is less thanthe pressure of the fluid within control chamber 338 of accumulator 330.According to an exemplary embodiment, gas spring 300 responds to aninput from an obstacle at a second spring rate where the pressure of thefluid within spring chamber 328 and working chamber 332 is greater thanthe pressure of the fluid within control chamber 338 of accumulator 330.Gas spring 300 having first and second spring rates is intended toreduce the peak forces on the vehicle thereby improving the ride qualityand durability. According to an exemplary embodiment, the second springrate is lower (i.e. softer, less harsh, etc.) than the first spring ratesuch that occupants within the vehicle are at least partially isolatedfrom larger input forces. According to an exemplary embodiment, thethreshold between the first spring rate and the second spring rate maybe tuned to adjust the response of gas spring 300 for a particularvehicle or application.

The pressurized fluid within working chamber 332 overcomes thepressurized fluid within control chamber 338 thereby deflecting bladder336, changing the volume of working chamber 332, and generating thesecond spring rate. The difference between the pressure of the fluidwithin working chamber 332 and control chamber 338 is specified toproduce a spring force curve for gas spring 300 having particularcharacteristics (e.g., a particular force for which gas spring 300transitions from the first spring rate to the second spring rate, etc.).According to an exemplary embodiment, the difference between thepressure of the fluid within working chamber 332 and control chamber 338is approximately 48 pounds per square inch.

According to an exemplary embodiment, gas spring 300 and accumulator 330are coupled to a valve assembly, shown as valve assembly 340. Valveassembly 340 facilitates increasing or decreasing the pressure withinspring chamber 328 and working chamber 332. According to an exemplaryembodiment, valve assembly 340 maintains the pressure differentialbetween working chamber 332 and control chamber 338. The pressuredifferential between working chamber 332 and control chamber 338 affectsthe spring force response curve of gas spring 300 (e.g., the force wheregas spring 300 changes from a first to a second spring rate). Valveassembly 340 maintains the pressure differential between the accumulatorand gas spring to provide a consistent response curve gas spring 300even under different operating temperatures, payloads, ride heights, orstill other conditions. Maintaining the pressure differential whileadding or removing fluid from spring chamber 328 accommodates changes tothe ride height of the vehicle without jeopardizing ride quality or thepreferred response curve of gas spring 300. It should be understood thatsuch an increase or decrease in pressure may occur by increasing ordecreasing the amount of fluid within spring chamber 328 and workingchamber 332 (e.g., where the fluid is a compressible gas).

Various factors affect the ride height of a vehicle. By way of example,gas spring 300 may be filed to a first pressure with a first amount offluid at a first temperature. Operating conditions of the vehicle (e.g.,operating in an environment at a temperature below the firsttemperature, etc.) may alter the pressure of the fluid within springchamber 328. The load of the vehicle may also impact the pressure of thefluid within spring chamber 328. By way of example, a greater payloadmay compress the gas spring to a pressure greater than an initialpressure. According to an exemplary embodiment, the pressure of thefluid within spring chamber 328 is adjustable to maintain a preferredride height of the vehicle when operating under these or otherconditions.

Valve assembly 340 is manually engageable, according to an exemplaryembodiment. By way of example, an operator may interface with acontroller (e.g., a switch, a lever, etc.) that is in communication witha flow control device (e.g., a solenoid, a valve, etc.) coupled to valveassembly 340. The operator may engage valve assembly 340 afteridentifying a change in the ride height (e.g., visually) or in responseto an indication (e.g., from a warning light, etc.) of a vehiclecharacteristic (e.g., a ride height, payload, tire pressure,temperature, or other operating condition).

According to an alternative embodiment, valve assembly 340 is at leastpartially automatically controlled as part of a ride height controlscheme. By way of example, a sensor (e.g., a ride height sensor, atemperature sensor, a tire pressure sensor, a spring pressure sensor, anaccumulator pressure sensor, a payload sensor, etc.) may provide asensor signal to a controller. The controller receives the sensorsignal, evaluates whether to adjust the ride height, and provides asignal to a flow device (e.g., a pump, a solenoid, a valve, etc.)configured to increase or decrease the pressure within spring chamber328. According to an exemplary embodiment, the controller operates on acontinuous feedback loop thereby continuously monitoring and regulatingthe ride height of the vehicle. According to an alternative embodiment,the controller monitors the ride height of the vehicle at discrete timeintervals (e.g., multiple times a day, before a shift, after a shift,after a change in payload, etc.). According to still another alternativeembodiment, valve assembly 340 is automatically controlled under normaloperating conditions but includes a manual override (e.g., to allow forcompression of gas spring 300 during transportation of the vehicle, toincrease the ride height to traverse rough terrain, etc.).

As shown in FIG. 3, valve assembly 340 is coupled to a fluid device(e.g., a pump, a reservoir, etc.) with a first line 342. It should beunderstood that valve assembly 340 may receive pressurized fluid flowfrom the fluid device while increasing the ride height or may providepressurized flow from gas spring 300 while lowering the ride height. Thefluid device may be selectively coupled to control chamber 338 toestablish an initial pressure of control chamber 338 (e.g., a pressurethat relates to the force where gas spring 300 transitions from thefirst spring rate to the second spring rate). According to an exemplaryembodiment, the fluid device increases the pressure of the fluid withincontrol chamber 338 thereby increasing the force required for gas spring300 to provide the second spring rate. According to an alternativeembodiment, the fluid device decreases the pressure of the fluid withincontrol chamber 338 thereby reducing the force required for gas spring300 to provide the second spring rate.

Valve assembly 340 may be also coupled to a port 324 of gas spring 300with a second line 344. According to an exemplary embodiment, port 324is in fluid communication with spring chamber 328 of tubular member 312and working chamber 332 of accumulator 330. As shown in FIG. 3, valveassembly 340 is coupled to a port 325 of accumulator 330 with a thirdline 346. According to an exemplary embodiment, port 325 is in fluidcommunication with control chamber 338 of accumulator 330. It should beunderstood that various internal chambers of valve assembly 340 are influid communication with spring chamber 328, working chamber 332, andcontrol chamber 338 through second line 344 and third line 346.According to an alternative embodiment, the valve assembly is integratedwith the gas spring (e.g., to the base) thereby reducing the need forintermediate piping. According to still another alternative embodiment,the piping is integrally formed with the gas spring to allow fordifferential placement of the valve assembly.

Referring next to the exemplary embodiment shown in FIG. 4, a valveassembly, shown as valve assembly 400, includes a solenoid 410, asolenoid block 420, and a valve block 430. According to an alternativeembodiment, valve assembly 400 does not include solenoid 410. Thesolenoid block 420 includes an input 412 that sends and receiveselectrical signals. As shown in FIG. 4, solenoid block 420 includes aninput 422 configured to interface with a flow device (e.g., a pump, areservoir, etc.). Valve block 430 includes body member 432 that definesan aperture, shown as port 434. According to an exemplary embodiment,port 434 engages an internal chamber of a spring (e.g., a gas spring).Valve block 430 may further define a second aperture configured toengage a control chamber of an accumulator. According to an exemplaryembodiment, valve assembly 400 includes an arrangement of individualcheck valves that provide a pressure offset between a plurality ofoutput ports. The valve assembly 400 may be implemented as part of avehicle suspension system to maintain a pressure differential betweendifferent components (e.g., the control chamber of a reservoir and aninternal chamber of a gas spring). According to an exemplary embodiment,a constant pressure differential during ride height adjustmentsfacilitates the consistent application of the second spring rate by thegas spring.

According to the exemplary embodiment shown in FIGS. 5-11, a valveassembly, shown as valve assembly 500, includes a valve body 510 thatdefines a first port, shown as accumulator port 520, a second port,shown as spring port 530, and a third port, shown as flow device port540. Accumulator port 520 is configured to be coupled to a controlchamber of a gas spring reservoir, spring port 530 is configured to becoupled to a spring chamber of the gas spring, and flow device port isconfigured to be coupled to a flow device (e.g., pump, reservoir, etc.),according to an exemplary embodiment. Such coupling may occur withintermediate lines. According to an alternative embodiment, valve body510 of valve assembly 500 may be coupled (e.g., bolted, welded,integrally formed with) a gas spring. The gas spring may includeinternal flow passages that place the various ports and components ofvalve assembly 500 in fluid communication with the spring chamber andthe control chamber, or external lines may otherwise couple valveassembly 500 with the gas spring, according to various alternativeembodiments. According to an exemplary embodiment, accumulator port 520,spring port 530, and flow device port 540 are marked with a marking orindicia (e.g., a stamp, a label, etc.) that indicates which line tocouple with the particular port of valve assembly 500.

Referring again to FIGS. 5-11, valve assembly 500 includes a pluralityof check valves positioned within valve body 510. According to anexemplary embodiment, valve assembly 500 includes a first check valve552, a second check valve 554, a third check valve 556, and a fourthcheck valve 558. As shown in FIGS. 5-7, first check valve 552 and secondcheck valve 554 are positioned along a flow path between flow deviceport 540 and an accumulator manifold 522. Accumulator manifold 522extends through valve body 510 and is in fluid communication withaccumulator port 520. As shown in FIGS. 5-7, third check valve 556 andfourth check valve 558 are positioned along a flow path between flowdevice port 540 and a spring manifold 532. Spring manifold 532 extendsthrough valve body 510 and is fluid communication with spring port 530.As shown in FIGS. 5-7, flow device port 540 is in fluid communicationwith each of first check valve 552, second check valve 554, third checkvalve 556, and fourth check valve 558 via a common flow device manifold542.

According to an exemplary embodiment, first check valve 552, secondcheck valve 554, third check valve 556, and fourth check valve 558 arearranged in a parallel check valve circuit. First check valve 552,second check valve 554, third check valve 556, and fourth check valve558 provide a pressure offset between accumulator port 520 and springport 530. According to an exemplary embodiment, first check valve 552and fourth check valve 558 have a first crack pressure whereas secondcheck valve 554 and third check valve 556 have a second crack pressure.It should be understood that check valves are biased toward a closedposition. Application of a fluid having a pressure greater than thecrack pressure for the check valve opens the check valve and allows afluid to flow therethrough. According to an exemplary embodiment, thesecond crack pressure is greater than the first crack pressure. By wayof example, the first crack pressure may be two pounds per square inchand the second crack pressure may be fifty pounds per square inch. Thedifferential between the first crack pressure and the second crackpressure is related (e.g., equal) to a difference in the fluid pressureat accumulator port 520 and spring port 530.

Referring again to the exemplary embodiment shown in FIGS. 10-11, firstcheck valve 552, second check valve 554, third check valve 556, andfourth check valve 558 are unidirectional such that flow occurs througheach check valve only along an orientation direction. As shown in FIGS.10-11, first check valve 552 is positioned to allow fluid flow from flowdevice manifold 542 to accumulator manifold 522; second check valve 554is positioned to allow fluid flow from accumulator manifold 522 to flowdevice manifold 542; third check valve 556 is positioned to allow fluidflow from flow device manifold 542 to spring manifold 532; and fourthcheck valve 558 is positioned to allow fluid flow from spring manifold532 to flow device manifold 542.

Referring again to the exemplary embodiment shown in FIG. 5, valve body510 includes a plurality of subcomponents coupled together withfasteners (e.g., bolts, screws, etc.). According to an alternativeembodiment, the subcomponents may be otherwise coupled together (e.g.,welded, adhesively secured, etc.). According to an exemplary embodiment,valve body 510 includes a first body portion, shown as flow deviceportion 512, a second body portion, shown as check valve portion 514,and a third body portion, shown as port portion 516. The plurality ofsubcomponents may facilitate manufacturing and maintenance of valveassembly 500. According to an exemplary embodiment, flow device manifold542 is defined (e.g., machined, cut, etc.) into flow device portion 512,apertures are defined for the check valves within check valve portion514, and the manifolds are defined within port portion 516. The checkvalves are positioned within the corresponding apertures within checkvalve portion 514, and the fasteners are positioned within apertures(e.g., threaded holes, etc.) to secure the subcomponents of valve body510 together. A seal or a sealing compound may be positioned betweenadjacent faces of the various subcomponents to prevent pressurized fluidfrom leaking out of valve body 510.

Referring next to the exemplary embodiment shown in FIGS. 12-14, avehicle suspension, shown as vehicle suspension 600 includes valveassembly 500; a spring, shown as gas spring 610; a reservoir, shown asaccumulator 620; and a flow control valve, shown as solenoid assembly630. As shown in FIG. 12, gas spring 610 includes a tubular member 612,a plunger 614 positioned within tubular member 612, and a rod coupled toplunger 614 and extending through an end of tubular member 612.According to an exemplary embodiment, gas spring 610 is coupled to thechassis (e.g., frame rail, hull, etc.) and a moveable suspensioncomponent (e.g., a wheel-end, etc.). As shown in FIG. 12, an innerportion of tubular member 612 and plunger 614 define a spring chamber618. According to an exemplary embodiment, accumulator 620 includes ahousing 622 and a bladder 624. Bladder 624 separates an inner volume ofhousing 622 into a working chamber 626 and a control chamber 628.Accumulator port 520 is coupled to control chamber 628 of accumulator620 with a line 662, and spring port 530 is coupled to spring chamber618 and working chamber 626 with a line 664. It should be understoodthat valve assembly 500 is in fluid communication with accumulator 620and gas spring 610 via line 662 and line 664. According to an exemplaryembodiment, a third line 666 couples valve assembly 500 to a second gasspring such that valve assembly 500 may maintain a pressure differentialfor multiple gas spring assemblies. As shown in FIGS. 12-14, a pressuretransducer 668 allows for the release of pressure from line 662 (e.g.,for service).

According to an exemplary embodiment, solenoid assembly 630 comprises atwo position directional control valve that includes a valve gate 632,an actuator 634, and a biasing member 636 (e.g., a spring, etc.).Biasing member 636 applies a biasing force and positions valve gate 632toward a first position where a check valve obstructs fluid flow fromvalve assembly 500 toward gas spring 610. Actuator 634 is configured toovercome the biasing force applied by biasing member 636 and actuatevalve gate 632 into a second position. Fluid flow may occur betweenvalve assembly 500 and gas spring 610 when valve gate 632 is in thesecond position, according to an exemplary embodiment. Solenoid assembly630 normally acts as a check valve to prevent fluid that may otherwiseflow from control chamber 628 through valve assembly 500 and into springchamber 618 along an undesired short circuit.

According to an exemplary embodiment, the pressure of the fluid withincontrol chamber 628 is greater than the pressure of fluid within springchamber 618. As plunger 614 and rod 616 extend within tubular member612, the pressure of the fluid within spring chamber 618 decreases.Where the pressure within spring chamber 618 is greatly reduced (e.g.,during full rebound) and the fluid within control chamber 628 ispressurized, the pressurized fluid from control chamber 628 may flowthrough line 662, overcome the crack pressure of second check valve 554,flow through flow device manifold 542, overcome the crack pressure ofthird check valve 556, and flow into spring chamber 618 through line 664(i.e. pressurized fluid from control chamber 628 may short circuitacross the larger crack pressure check valves and into spring chamber618). According to an exemplary embodiment, solenoid assembly 630prevents such flow.

According to the exemplary embodiment shown in FIG. 13, the ride heightof the vehicle is elevated by the application of pressurized fluid toflow device port 540. The ride height of the vehicle may be increased byincreasing the pressure of the fluid within spring chamber 618.According to an exemplary embodiment, valve assembly 500 facilitatesincreasing the pressure of the fluid within spring chamber 618 whilemaintaining the pressure differential between spring chamber 618 andcontrol chamber 628. According to an exemplary embodiment, the pressureof the fluid within control chamber 628 is greater than the pressure ofthe fluid within spring chamber 618. Such an increase in the ride heightof the vehicle may occur to compensate for an increase in the sprungweight of the vehicle (e.g., an increased payload, etc.), a decrease intemperature of the operating environment (e.g., the vehicle travels to alocation having a decreased temperature), in order to prepare thevehicle for transport, or for still another reason.

As shown in FIG. 13, the ride height of the vehicle is increased byapplying a fluid having a pressure that is greater than the pressure ofthe fluid within spring chamber 618 (i.e. a high pressure fluid) to flowdevice port 540. According to an exemplary embodiment, the initialpressure of the fluid within spring chamber 618 is 1,000 pounds persquare inch and the fluid applied to flow device port 540 has a pressureof 1,100 pounds per square inch. The pressurized fluid flows into flowdevice manifold 542 where it interacts with first check valve 552,second check valve 554, third check valve 556, and fourth check valve558. According to an exemplary embodiment first check valve 552 andthird check valve 556 have an orientation direction that allows fluid toflow only from flow device manifold 542 to spring manifold 532 andaccumulator manifold 522. The high pressure fluid (e.g., 1,100 poundsper square inch) overcomes the crack pressures of first check valve 552(e.g., 2 pounds per square inch) and third check valve 556 (e.g., 50pounds per square inch) and flows into spring manifold 532 andaccumulator manifold 522. The pressure of the fluid within springmanifold 532 and accumulator manifold 522 may be lower than the pressureof the fluid at flow device manifold 542 due to interaction with thecheck valves.

According to an exemplary embodiment, the pressure of the fluid withinspring manifold 532 and accumulator manifold 522 is reduced by an amountequal to the crack pressure of third check valve 556 and first checkvalve 552, respectively. By way of example, a fluid pressure of 1,100pounds per square inch may be reduced to 1,050 pounds per square inch atspring manifold 532 where third check valve 556 has a crack pressure of50 pounds per square inch and reduced to 1,098 pounds per square inch ataccumulator manifold 522 where first check valve 552 has a crackpressure of 2 pounds per square inch. According to an exemplaryembodiment, the differential in pressures between spring manifold 532and accumulator manifold 522 maintains a pressure differential betweenspring chamber 618 and control chamber 628 while providing fluid flowinto both chambers (e.g., to raise the ride height of the vehicle).According to an alternative embodiment, the differential in pressuresbetween spring manifold 532 and accumulator manifold 522 increases thepressure (i.e. charges) within spring chamber 618 and control chamber628 while maintaining a preferred pressure offset (e.g., 48 pounds persquare inch).

Referring next to the exemplary embodiment shown in FIG. 14, the rideheight of the vehicle is reduced by the application of a low pressurefluid to flow device port 540. The ride height of the vehicle may belowered by decreasing the pressure of the fluid within spring chamber618. According to an exemplary embodiment, valve assembly 500facilitates decreasing the pressure of the fluid within spring chamber618 while maintaining the pressure differential between spring chamber618 and control chamber 628. Such a reduction in the ride height of thevehicle may occur to compensate for a decrease in the sprung weight ofthe vehicle (e.g., a decreased payload, etc.), an increase intemperature of the operating environment (e.g., the vehicle travels to alocation having a decreased temperature), in order to ready the vehicleafter transport, or for still another reason.

As shown in FIG. 14, the ride height of the vehicle is decreased byexposing flow device port 540 to a fluid having a pressure lower thanthe pressure of the fluid within spring chamber 618 (i.e. a low pressurefluid). According to an exemplary embodiment, the initial pressure ofthe fluid within spring chamber 618 is 1,000 pounds per square inch andthe fluid applied to flow device port 540 has a pressure of 900 poundsper square inch. The pressurized fluid from spring chamber 618 interactswith third check valve 556 and fourth check valve 558, and thepressurized fluid from control chamber interacts with first check valve552 and second check valve 554. According to an exemplary embodiment,second check valve 554 and fourth check valve 558 have an orientationdirection that allows fluid to flow only from spring manifold 532 andaccumulator manifold 522 to flow device manifold 542. The high-pressurefluid from spring chamber 618 and control chamber 628 overcomes thecrack pressure of second check valve 554 (e.g., 50 pounds per squareinch) and fourth check valve 558 (e.g., 2 pounds per square inch) andflows out flow device port 540 through flow device manifold 542. Thepressure of the fluid within spring chamber 618 is reduced therebylowering the ride height of the vehicle. According to an exemplaryembodiment, valve assembly 500 reduces pressure of the fluid withinspring chamber 618 while maintaining the offset pressure between springchamber 618 and control chamber 628 (e.g., a pressure offset of 48pounds per square inch).

According to an exemplary embodiment, actuation of solenoid assembly 630and the application of a fluid having preferred characteristics (e.g., alow pressure, a high pressure, etc.) to flow device port 540 occurselectronically. By way of example, a controller may send a signal tosolenoid assembly 630. The controller may also send a signal to engage afluid pump, a flow valve disposed between a reservoir and flow deviceport 540, or otherwise interact with another component. Upon actuation,the pump or valve are configured to expose flow device port 540 to thefluid having the appropriate characteristics (e.g., high pressure fluidto increase the ride height, low pressure fluid to decrease the rideheight, etc.). According to an exemplary embodiment, the electroniccontrol occurs as part of a ride height control scheme. A controllerevaluates signals from a ride height, temperature, load, pressure, orother type of sensor and determines whether the ride height is within apreferred range (e.g., as specified in a parameter either upon initialmanufacture, as specified in a parameter by an operator, etc.).According to an alternative embodiment, the electronic control systemincludes an operator input. By way of example an operator may engage aswitch that is coupled to a controller, the controller configured toevaluate signals from the switch and send signals to actuate the fluidpump, flow valve, or other device. According to still anotheralternative embodiment, an operator manually engages solenoid assembly630 (e.g., by pressing a button positioned thereon) and manuallyinteracts with the pump, valve, or other device to expose flow deviceport 540 to the fluid having the appropriate characteristics.

As shown in FIG. 15, the pressure drop of a fluid flow through firstcheck valve 552, second check valve 554, third check valve 556, andfourth check valve 558 is related to the flow rate of the fluid. Itshould be understood that the flow rate of the fluid may be regulated invarious ways and is related to a pressure differential, among othercharacteristics of the fluid applied to the flow device port. For flowrates below an orifice line 700, the pressure drop of a fluid flowingthrough a valve having a crack pressure of 50 pounds per square inch isapproximately 50 pounds per square inch (e.g., within 5 pounds persquare inch). In this region, the pressure drop remains approximatelyconstant for different flow rates. According to an exemplary embodiment,a vehicle suspension system provides a fluid flow into a flow deviceport of a valve assembly at a flow rate below orifice line 700 such thatthe valve assembly provides a predetermined pressure offset (e.g., 48pounds per square inch). According to an exemplary embodiment, firstcheck valve 552 and fourth check valve 558 have a crack pressure andcorresponding pressure drop of two pounds per square inch and secondcheck valve 554 and third check valve 556 have a crack pressure andcorresponding pressure drop of fifty pounds per square inch. The valveassembly may include check valves having still other crack pressures andcorresponding pressure drops to provide still other pressure offsetsbetween two chambers (e.g., a spring chamber and a control chamber,etc.).

In still another contemplated embodiment, a gas spring further includesat least one port that may be opened to allow another fluid (e.g.,hydraulic oil, water, etc.) to be provided to or from an internal volumeof the gas spring. The internal volume for hydraulic fluid is separatedfrom the spring chamber that contains gas. In such contemplatedembodiments, adding or removing hydraulic fluid from the internal volumechanges the overall length of the gas spring and may also increase ordecrease the ride height of the vehicle.

The construction and arrangements of the damper, as shown in the variousexemplary embodiments, are illustrative only. Although only a fewembodiments have been described in detail in this disclosure, manymodifications are possible (e.g., variations in sizes, dimensions,structures, shapes and proportions of the various elements, values ofparameters, mounting arrangements, use of materials, colors,orientations, etc.) without materially departing from the novelteachings and advantages of the subject matter described herein. Someelements shown as integrally formed may be constructed of multiple partsor elements, the position of elements may be reversed or otherwisevaried, and the nature or number of discrete elements or positions maybe altered or varied. The order or sequence of any process, logicalalgorithm, or method steps may be varied or re-sequenced according toalternative embodiments. Other substitutions, modifications, changes andomissions may also be made in the design, operating conditions andarrangement of the various exemplary embodiments without departing fromthe scope of the present invention.

What is claimed is:
 1. A valve assembly for a suspension system,comprising: a housing including a first port, a second port, and a thirdport, the housing defining a first flow path extending between the thirdport and the first port and a second flow path extending between thethird port and the second port; a first check valve having a first crackpressure positioned within the housing along the first flow path; and asecond check valve having a second crack pressure positioned within thehousing along the second flow path, wherein a difference between thefirst crack pressure and the second crack pressure provides acorresponding difference in pressures at the first port and the secondport.
 2. The valve assembly of claim 1, wherein the first check valveand the second check valve open along the first flow path and the secondflow path toward the third port to exhaust pressure from the first portand the second port.
 3. The valve assembly of claim 1, furthercomprising a third check valve having a third crack pressure andpositioned within the housing along the first flow path and a fourthcheck valve having a fourth crack pressure and positioned within thehousing along the second flow path.
 4. The valve assembly of claim 3,wherein the first check valve and the second check valve open along thefirst flow path and the second flow path toward the third port toexhaust pressure from the first port and the second port.
 5. The valveassembly of claim 4, wherein the third check valve and the fourth checkvalve open along the first flow path and the second flow path toward thefirst port and the second port to supply pressure from the third port.6. The valve assembly of claim 3, wherein the first crack pressure isequal to the fourth crack pressure and the second crack pressure isequal to the third crack pressure.
 7. The valve assembly of claim 6,wherein the second crack pressure is greater than the first crackpressure.
 8. The valve assembly of claim 7, wherein the first crackpressure is about two pounds per square inch and the second crackpressure is about fifty pounds per square inch.
 9. The valve assembly ofclaim 3, wherein the housing further defines: a first manifold thatcouples the first port to the first check valve and the third checkvalve; and a second manifold that couples the second port to the secondcheck valve and the fourth check valve.
 10. The valve assembly of claim9, wherein the housing defines a third manifold that couples the thirdport to the first check valve, the second check valve, the third checkvalve, and the fourth check valve.
 11. A suspension assembly for avehicle, comprising: a gas spring, comprising: a tubular housing; aplunger positioned within the tubular housing, the plunger and an innersurface of the tubular housing defining a spring volume; a reservoirincluding a housing that defines an inner volume and a flexible membercoupled to the housing, the flexible member separating the inner volumeinto a working volume and a control volume; and a conduit coupling thetubular housing to the reservoir such that the spring volume is in fluidcommunication with the working volume; and a valve assembly, comprising:a first check valve having a first crack pressure positioned along afirst flow path between the spring volume and a flow device port; and asecond check valve having a second crack pressure positioned along asecond flow path between the control volume and the flow device port,wherein the valve assembly provides an offset pressure between thespring volume and the control volume to maintain a response curve of thegas spring for different ride heights of the vehicle.
 12. The suspensionassembly of claim 11, wherein the first check valve and the second checkvalve open along the first flow path and the second flow path toward theflow device port to exhaust pressure from the spring volume and thecontrol volume.
 13. The suspension assembly of claim 11, furthercomprising a third check valve having a third crack pressure andpositioned along the first flow path and a fourth check valve having afourth crack pressure and positioned along the second flow path.
 14. Thesuspension assembly of claim 13, wherein the first check valve and thesecond check valve open along the first flow path and the second flowpath toward the flow device port to exhaust pressure from the springvolume and the control volume.
 15. The suspension assembly of claim 14,wherein the third check valve and the fourth check valve open along thefirst flow path and the second flow path toward the spring volume andthe control volume to supply pressure from the flow device port.
 16. Thesuspension assembly of claim 13, wherein the first crack pressure isequal to the fourth crack pressure and the second crack pressure isequal to the third crack pressure.
 17. The suspension assembly of claim16, wherein the second crack pressure is greater than the first crackpressure.
 18. The suspension assembly of claim 17, wherein the firstcrack pressure is about two pounds per square inch and the second crackpressure is about fifty pounds per square inch.
 19. The suspensionassembly of claim 11, further comprising a flow control valve disposedalong the first flow path between the spring volume and the first checkvalve, the flow control valve positioned to prevent short circuit fluidflow from the control volume to the spring volume across the valveassembly.
 20. A method for changing a ride height of a vehicle,comprising: providing a gas spring including a housing that defines aspring volume and an accumulator that defines a control volume;providing a valve assembly including a port and a plurality of checkvalves having different crack pressures; exposing the port to apressurized fluid associated with a flow device; and maintaining apressure differential between the spring volume and the control volume,the pressure differential corresponding to a difference in the crackpressures of the plurality of check valves.